The Ex-B (explosive-bolt) is an alien experiment that involves equipping the guardian drone model of defensive robot with a cannon that fires spheres of energy that explode upon impact. The Ex-B has a very long range, and if aimed manually, can be used as an effective sniper. The Ex-B can be shot effectively underwater without adverse effects. This variation allows the fired projectile to bounce off solid objects once.
The drone cannon, however, is an ineffective V.A.T.S. weapon, as the fired projectiles will arc toward their targets; since the game does not compensate for gravity in V.A.T.S., this can leave projectiles several meters away from their intended targets.
In the southern area of the weapons lab, there is a room where one can use a nearby button to spawn-in brahmin for the drones to kill (not the room next to the shooting range, but the room next to the weapons cache). Enter the room and kill the drone for the weapon. There is also a second one in the same room that is automatically activated when the first is destroyed.
PCPlaystation 3Xbox 360 When shot, the projectile will occasionally pass through walls or the floor and do nothing. [verified]
PCPlaystation 3Xbox 360 In some accounts, when shot, the projectile will just disappear as soon as it hits the target, damaging it but not exploding. [verified]
PCXbox 360 When shot into deep water, the projectile will disappear, and then reappear and seemingly "float" in place on the surface without exploding. Projectiles fired onto the floating projectile will attach and stack, also without exploding. [verified]
PCPlaystation 3Xbox 360 In V.A.T.S. mode, the Ex-B seems to aim like a normal drone cannon, landing short of the enemy as if expecting the projectile to bounce. [verified]
Playstation 3 On some occasions, the cannon will fire the projectile but will bounce off surfaces and not explode. [verified]